Expose APIs to access supported feature flags

With this, we can read the features supported by the node
as announced in node and channel announcements, within
an init message, and within a BOLT 11 invoice.

We write a small integration test to assert that, at minimum,
certain features are supported by default, for example, keysend
support.

Author: enigbe

src/lib.rs

@@ -151,7 +151,8 @@ use lightning::impl_writeable_tlv_based;
 use lightning::ln::chan_utils::FUNDING_TRANSACTION_WITNESS_WEIGHT;
 use lightning::ln::channel_state::{ChannelDetails as LdkChannelDetails, ChannelShutdownState};
 use lightning::ln::channelmanager::PaymentId;
-use lightning::ln::msgs::SocketAddress;
+use lightning::ln::msgs::{BaseMessageHandler, SocketAddress};
+use lightning::ln::peer_handler::CustomMessageHandler;
 use lightning::routing::gossip::NodeAlias;
 use lightning::sign::EntropySource;
 use lightning::util::persist::KVStoreSync;
@@ -160,6 +161,9 @@ use lightning_background_processor::process_events_async;
 pub use lightning_invoice;
 pub use lightning_liquidity;
 pub use lightning_types;
+use lightning_types::features::{
+	Bolt11InvoiceFeatures, ChannelFeatures, InitFeatures, NodeFeatures,
+};
 use liquidity::{LSPS1Liquidity, LiquiditySource};
 use lnurl_auth::LnurlAuth;
 use logger::{log_debug, log_error, log_info, log_trace, LdkLogger, Logger};
@@ -1949,6 +1953,63 @@ impl Node {
 			Error::PersistenceFailed
 		})
 	}
+
+	/// Return the features used in node announcement.
+	pub fn node_features(&self) -> NodeFeatures {
+		let gossip_features = match self.gossip_source.as_gossip_sync() {
+			lightning_background_processor::GossipSync::P2P(p2p_gossip_sync) => {
+				p2p_gossip_sync.provided_node_features()
+			},
+			lightning_background_processor::GossipSync::Rapid(_) => NodeFeatures::empty(),
+			lightning_background_processor::GossipSync::None => {
+				unreachable!("We must always have a gossip sync!")
+			},
+		};
+		self.channel_manager.node_features()
+			| self.chain_monitor.provided_node_features()
+			| self.onion_messenger.provided_node_features()
+			| gossip_features
+			| self
+				.liquidity_source
+				.as_ref()
+				.map(|ls| ls.liquidity_manager().provided_node_features())
+				.unwrap_or_else(NodeFeatures::empty)
+	}
+
+	/// Return the node's init features.
+	pub fn init_features(&self) -> InitFeatures {
+		let gossip_init_features = match self.gossip_source.as_gossip_sync() {
+			lightning_background_processor::GossipSync::P2P(p2p_gossip_sync) => {
+				p2p_gossip_sync.provided_init_features(self.node_id())
+			},
+			lightning_background_processor::GossipSync::Rapid(_) => InitFeatures::empty(),
+			lightning_background_processor::GossipSync::None => {
+				unreachable!("We must always have a gossip sync!")
+			},
+		};
+		self.channel_manager.init_features()
+			| self.chain_monitor.provided_init_features(self.node_id())
+			| self.onion_messenger.provided_init_features(self.node_id())
+			| gossip_init_features
+			| self
+				.liquidity_source
+				.as_ref()
+				.map(|ls| ls.liquidity_manager().provided_init_features(self.node_id()))
+				.unwrap_or_else(InitFeatures::empty)
+	}
+
+	/// Return the node's channel features.
+	pub fn channel_features(&self) -> ChannelFeatures {
+		self.channel_manager.channel_features()
+	}
+
+	/// Return the node's BOLT 11 invoice features.
+	pub fn bolt11_invoice_features(&self) -> Bolt11InvoiceFeatures {
+		// bolt11_invoice_features() is not public because feature
+		// flags can vary due to invoice type, so we convert from
+		// context.
+		self.channel_manager.init_features().to_context()
+	}
 }
 
 impl Drop for Node {

tests/integration_tests_rust.rs

@@ -2805,3 +2805,37 @@ async fn splice_in_with_all_balance() {
 	node_a.stop().unwrap();
 	node_b.stop().unwrap();
 }
+
+#[test]
+fn node_feature_flags() {
+	let (bitcoind, electrsd) = setup_bitcoind_and_electrsd();
+	let chain_source = random_chain_source(&bitcoind, &electrsd);
+	let config = random_config(true);
+	let node = setup_node(&chain_source, config);
+
+	// NodeFeatures
+	let node_features = node.node_features();
+	assert!(node_features.supports_variable_length_onion());
+	assert!(node_features.supports_payment_secret());
+	assert!(node_features.supports_basic_mpp());
+	assert!(node_features.supports_keysend());
+	assert!(node_features.supports_onion_messages());
+
+	// InitFeatures
+	let init_features = node.init_features();
+	assert!(init_features.supports_variable_length_onion());
+	assert!(init_features.supports_payment_secret());
+	assert!(init_features.supports_basic_mpp());
+	assert!(init_features.supports_onion_messages());
+
+	// ChannelFeatures (non-empty)
+	let _channel_features = node.channel_features();
+
+	// Bolt11InvoiceFeatures
+	let bolt11_features = node.bolt11_invoice_features();
+	assert!(bolt11_features.supports_variable_length_onion());
+	assert!(bolt11_features.supports_payment_secret());
+	assert!(bolt11_features.supports_basic_mpp());
+
+	node.stop().unwrap();
+}